1. Field of the Invention
The present invention relates to model vehicle systems, for example, model trains and accessories. More particularly, the invention relates to a power supply for a model vehicle system.
2. Description of Related Art
Model trains and accessories have been generally known for decades. In many model railway systems, model trains and accessories receive electrical power from a voltage that is applied to the tracks. A power supply is used to apply the voltage to the tracks, while contacts on the bottom of the train, or metallic wheels of the train, pick up the applied voltage for motors and other electrical components. The power supply may be used to control both the amplitude and polarity of the voltage, thereby controlling the speed and direction of the train. In HO systems, the voltage is typically a DC voltage. In O-gauge systems, the track voltage is typically an AC voltage transformed by a transformer in the power supply from a higher household voltage (e.g., 120 or 240 volts AC), to a reduced AC voltage (e.g., 0-18 volts AC).
Speed control for model vehicles on a model track may be accomplished by controlling the voltage supplied to the track. For example, in a typical O-gauge system operated in a conventional control mode, the speed may be controlled by adjusting a handle, lever, knob or other input adjuster on a power supply module, also called a power controller. The position of the input adjuster controls the magnitude of voltage supplied to the layout, via circuitry in the power controller. The higher the magnitude of the voltage applied to the system, the faster the train will travel, and vice versa. In known power supplies, the voltage adjuster for the power controller has a first position corresponding to zero volts or “OFF”, and a second position corresponding to a maximum voltage (e.g., 18-25 volts), or fully “ON”. The power controller is configured such that the voltage level is adjusted throughout the range of motion of the input adjuster, from zero to the maximum voltage. A user may thereby adjust the voltage supplied to the train system and the speed of the train by moving the adjuster, such as a lever or a knob, in either a first or second direction.
Notwithstanding their advantages, power controllers as known in the art are subject to certain limitations. For instance, in some O-gauge systems the electric motor is of the type that requires approximately six to nine volts to overcome starting resistance and begin moving. For example, for power supplies having an output range of zero to 18 volts, a voltage control adjuster needs to be moved roughly 40-50% of its available range of movement just to begin movement of the train. Consequently, only 50-60% of the available range of movement remains for the control of the speed. This reduced range of movement may result in reduced precision, resolution and overall control. An additional disadvantage related to this reduced range of movement is that long-time model railroad hobbyists have grown accustomed to using the entire range of movement path for speed control. Accordingly, known systems having a reduced useful range of movement may be a source of dissatisfaction for experienced hobbyists.
Accordingly, a need exists for a power controller for a model vehicle system that minimizes or eliminates one or more of the above-identified deficiencies.